Kidney transplant questions?

heres the details my grandpa is in stage 4 kidney disease and its not getting any better possibly worse im not sure if its getting worse or not it may be staying the same but my question for you guys is am i going to be able to give him one of my kidneys if the time comes im 18 year boy 19 in a couple days im in pritty good shape im on two diffrent blood pressure meds for my tourette's syndrome and thouse meds are tenex and topmax but both of them are offbrand i think thats all you need to know if im messing any thing just ask and ill fill it in ohh and my grandpa is in stage four kidney disease out of stage 5 and i dont wana see him on dialysis for a coupple years and if you guys know the cost of a kidney transplant that would be helpful thank you guys